142 THE ANIMAL PARASITES OF MAN 



this genus may be frequently referred to as Coccidium, strictly it 

 should be termed Eimeria, that name having priority. The name 

 of the disease resulting from the action of such parasites is, however, 

 established and remains as coccidiosis. 



Certain of the more important of the Coccidiidea may now be 

 considered. 



Genus. Eimeria, Aime Schneider, 1875. 



Syn. : Psorospermium, Rivolta, 1878 ; Cytospermium, Rivolta, 1878 ; Cocddium, 

 R. Leuckart, 1879 ; Pfeifferia, Labbe, 1894: Pfeifferelia, Labbe, 1899. 



The Eimeria belong to Leger's old family, the Tetrasporocystidae, 

 which comprises forms producing oocysts with four sporocysts, each 

 containing two sporozoites. The cysts are spherical or oval, as are 

 also usually the schizonts. The members of the genus are confined 

 chiefly to vertebrate hosts, the more important economically occurring 

 in mammals and birds. From the mammalian hosts very rarely the 

 parasites may reach man. Eimeria (Coccidium) avinm of wild birds 

 and poultry, and Eimerm stiedcc parasitic in rabbits, may be con- 

 sidered. There is a general similarity in their life-cycles and each is 

 of great practical importance. 



Eimeria avium, Silvestrini and Rivolta. 



Eimeria avium is responsible for fatal epizootics among game birds such as 

 grouse, pheasants and partridges, and domestic poultry such as fowls, ducks, pigeons 

 and turkeys, and can pass from any one of these hosts to any of the others with the 

 same effect. The organism is parasitic in the alimentary tract of the host, affecting 

 more ej^ecially the small intestine (duodenum) and the caeca, but in some cases 

 penetrating to the liver and multiplying there (as in turkeys), producing necrotic 

 cheesy patches, that ultimately become full of oocysts. The gut is rendered very 

 frail by the action of the parasites, its mucous membrane is greatly injured, and 

 is often reduced to an almost structureless pulp, riddled with parasites (fig. 68). 

 Infection is conveyed from host to host by the ingestion of food or drink contamin- 

 ated with the oocysts voided in the fasces of infected birds. Oval oocysts from 24 ju to 

 35 ;x long and from 14^ to 20 /j. broad are the means of infection. The oocysts 

 develop internally four sporocysts or spores, from each of which two sporozoites are 

 produced. The life-history 1 presents two phases: (i) The asexual multiplicative 

 phase, schizogony, for the increase in numbers of the parasites within the same host ; 

 (2) the reproductive phase, following the formation of gametes (gametogony), leading 

 to the production of resistant oocysts, destined for the transference of the parasite 

 to new hosts (sporogony). 



The oocysts usually reach the duodenum unharmed, with food or drink. Under 



1 Fantham, H. B. (1910), "The Morphology and Life History of Eimeria ( Coccidium ) 

 avittin, a Sporozoon causing a fatal disease among young Grouse," Proc. ZooL Soc. Lend., 

 1910, pp. 672-691, 4 plates. Also Fantham, H. B. (1911), "Coccidiosis in British Game 

 Birds and Poultry," Journ, Econ. Biol., vi, pp. 75-96. 



